Syringe pump control systems and methods

ABSTRACT

Sensors are described that may be provided in a medication pump. A magnetic sensor detects rotation of an element that is rotated by a motor, where a magnet covers a portion of the element. A light sensor may also be provided that detects if a cartridge is present in a cartridge chamber. A medication cartridge includes an opaque area at its open end for use with the light sensor. Methods of using these sensors to operate the pump area also described.

This application is being filed concurrently with the following sixcommonly assigned patent applications: “Cartridge and Pump with AxialLoading” U.S. application Ser. No. 10/086,646, “Child Safety Cap forSyringe Pump” U.S. application Ser. No. 10/086,993, now abandoned,“Insulin Pump Having Missed Meal Bolus Alarm” U.S. application Ser No.10/087,460, now U.S. Pat. No. 6,744,350, “Programmable Medical InfusionPump Displaying a Banner” U.S. application Ser. No. 10/087,205,“Programmable Insulin Pump” U.S. application Ser. No. 10/086,641, nowU.S. Pat. No. 6,852,104, and “Programmable Medical Infusion Pump” U.S.application Ser. No. 10/087,449. The disclosures of these six patentapplications are hereby incorporated herein by reference in theirentirety.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to a medication pump and a cartridge foruse in a medication pump, and methods for using the same. Moreparticularly, the present invention is particularly useful in thecontext of portable medication pumps that automatically dischargemedication from a medication cartridge.

Various ambulatory or portable medical devices are known for treatingpatients at a remote site away from the caregiver or clinician office.One example of an ambulatory medical device is a drug delivery device,such as a drug pump, for providing periodic or continuous drug deliveryto the patient when the patient is away from the caregiver's office.Ambulatory drug pumps are shown for example in U.S. Pat. Nos. 4,559,038,4,731,058, 5,531,697, 5,389,078 and 5,695,473, the disclosures of whichare hereby incorporated by reference. Drug pumps may be used to deliverinsulin and many other medications.

Medication pumps are known that use a piston-like arrangement to pushmedication out of a cylindrical medication reservoir. The cylindricalmedication reservoir may be provided within a cylindrical barrel, wherea plunger pushes medication out of the reservoir, and may be called asyringe or cartridge. Drug pumps typically have a delivery conduit forconnecting to the patient's body for delivery of the drug. An infusionset typically includes the delivery conduit, an access device forattaching the delivery conduit to the patient's body and an attachmentdevice for attaching the delivery conduit to a medication cartridge.Improved structures and methods are needed for filling medicationcartridges, loading medication cartridges, and sensing conditions withinmedication pumps.

SUMMARY OF THE INVENTION

The present invention relates to sensors that may be provided in amedication pump, methods for using a medication pump that includesoperational sensors, and a medication cartridge for use with themedication pump. In one embodiment, a medication pump includes a motorand a first element that is rotated by the motor, where the element hasa front face. A magnet is attached to the front face of the firstelement, but the magnet does not cover a portion of the front face. Amagnetic field sensor is spaced from an off-center location of themagnet, so that the sensor can detect the rotation of the element.

In another embodiment, a medication pump is provided with a light sensorto detect whether a medication cartridge is present in a cartridgechamber. The light sensor may include an emitter and a detectorpositioned at opposite ends of a chord through the cartridge chamber,where the chord passes through a portion of the medication cartridgewhen the medication cartridge is in the cartridge chamber. The chorddoes not pass through the drive rod.

In a method of loading a medication cartridge into a medication pumpaccording to one embodiment of the present invention, the medicationpump detects whether or not an old medication cartridge is present nearone end of a cartridge chamber, and then, if the old medicationcartridge is not present, the pump moves a drive rod to an initialloading position. The user is then prompted to insert a new medicationcartridge into the cartridge chamber. The initial loading position maybe determined based on the user's past history of cartridge fullness, sothat drive rod is conveniently located for attaching a cartridge.

In another embodiment of the invention, a medication cartridge isconfigured to be used with the light sensor. A cartridge barrel includesa cylindrical barrel wall having an open end and a closed end. A ridgeis defined on an interior face of the barrel wall, and the barrel wallis more opaque in the region extending from the ridge to the open endthan in at least a portion of a remainder of the barrel wall.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood by considering thedetailed description of various embodiments of the invention whichfollows in connection with the accompanying drawings.

FIG. 1 is a back, left perspective view of a syringe pump according toone embodiment of the present invention.

FIG. 2 is a front, left perspective view of a housing of the pump ofFIG. 1 with the bolus button, battery cap and pump cap removed, with thefront cover separated from the housing.

FIG. 3 is a front view of the pump of FIG. 1 showing the keypad anddisplay screen, where the pump is attached to an administration set.

FIG. 4 is a front view of the drive assembly components within the pumphousing for the pump of FIG. 1.

FIG. 5 is a front view of the drive assembly components within the pumphousing for the pump of FIG. 1 where the drive rod is partially advancedinto the cartridge chamber.

FIG. 6 is a cross-sectional view of the components of FIG. 5 along line6—6 of FIG. 5.

FIG. 7 is a cross-sectional view of the components of FIG. 5 along line7—7 of FIG. 5.

FIG. 8 is a front, right view of a drive rod of the pump of FIG. 1.

FIG. 9 is a front view of the drive assembly components within the pumphousing for the pump of FIG. 1 where the cartridge chamber is notpresent and a plunger is attached to the end of the drive rod.

FIG. 10 is a top view of the removable cartridge rod, plunger, andcartridge barrel of a cartridge for use in a syringe pump of oneembodiment of the present invention.

FIG. 11 is a top view showing the components of FIG. 10 where thecartridge rod is attached to the plunger and the plunger is positionedwithin the cartridge barrel.

FIG. 12 is a perspective end view of the removable cartridge rod of FIG.10.

FIG. 13 is a top perspective view of the removable cartridge rod of FIG.10.

FIG. 14 is a rear perspective view of the plunger of FIG. 10.

FIG. 15 is a front end perspective view of the cartridge barrel of FIG.10.

FIG. 16 is a back end perspective view of the cartridge barrel of FIG.10.

FIG. 17 is a top perspective view of a pump cap according to oneembodiment of the present invention.

FIG. 18 is a bottom perspective view of the pump cap of FIG. 17.

FIG. 19 is a top view of the pump cap of FIG. 17.

FIG. 20 is a cross-sectional view of the pump cap of FIG. 17 taken alongline 20—20 of FIG. 19.

FIG. 21 is a front view of the pump of FIG. 1 where a medicationcartridge is loaded in the cartridge chamber.

FIG. 22 is a cross-sectional view of the pump of FIG. 21 along line22—22 of FIG. 21.

FIG. 23 is an enlarged view of the pump components of FIG. 1 within thepump housing.

FIG. 24 is a front perspective view of an idler gear having a magneticflag according to one embodiment of the present invention.

FIG. 25 is a front perspective view of an idler gear circuit boardaccording to one embodiment of the present invention.

FIG. 26 is a side view of a bushing used to space the idler gear fromthe idler gear sensor according to one embodiment of the presentinvention.

FIG. 27 is a front view of a drive assembly chassis of the presentinvention.

FIG. 28 is a right view of the drive assembly chassis of FIG. 27.

FIG. 29 is a front perspective view of the drive assembly of the pump ofFIG. 1.

FIG. 30 is a block diagram of the components of the pump of FIG. 1.

FIG. 31 is a flowchart of the cartridge loading method of one embodimentof the present invention.

FIG. 32 is a flowchart of further cartridge loading steps of oneembodiment of the invention.

FIG. 33 is a flowchart of additional cartridge loading steps of oneembodiment of the present invention.

FIG. 34 is a right perspective view of the drive rod of FIG. 8.

FIG. 35 is a left front perspective view of a pump housing for the pumpof FIG. 1 without drive assembly components, where two circuit boardsare shown separated from the pump housing.

FIG. 36 is a front perspective view of one embodiment of a pump clip forattachment to the pump of FIG. 1, according to the present invention.

FIG. 37 is a rear perspective view of the pump clip of FIG. 36.

FIG. 38 is a bottom perspective view of a child safety pump cap coveraccording to one embodiment of the present invention.

FIG. 39 is a bottom view of the child safety pump cap cover of FIG. 38.

FIG. 40 is a side view of the child safety pump cap cover of FIG. 38.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE VARIOUS EMBODIMENTS

The present invention is believed to be applicable to a variety ofdevices, systems and methods for delivering medication using a syringeor cartridge and a pump. The invention has been found to be particularlyadvantageous in application environments where a cartridge is axiallyloaded into a pump. While the present invention is not so limited, anappreciation of various aspects of the invention is best gained througha discussion of various application examples operating in such anenvironment.

Various embodiments of the present invention will be described in detailwith reference to the drawings, where like reference numerals representlike parts and assemblies throughout the several views. Reference tovarious embodiments does not limit the scope of the invention, which islimited only by the scope of the claims attached hereto. Additionally,any examples set forth in this specification are not intended to belimiting and merely set forth some of the many possible embodiments forthe claimed invention.

FIG. 1 illustrates one particular embodiment of a syringe pump where asyringe or cartridge is axially loaded. The terms syringe and cartridgewill be used interchangeably to refer to a device having a hollow barrelfitted with a plunger. The pump 10 of FIG. 1 includes an outer pumphousing 14. A pump cap 16 covers an opening into a cartridge chamber 80(shown in FIG. 4) that receives a syringe or cartridge. The pump outerhousing 14 also includes a viewing window 20 into the cartridge chamber.The pump 10 also includes a battery cover 24.

Now referring to FIG. 2, the pump 10 is shown without the pump cap 16,revealing the opening 28 to the chamber 80. In addition, the battery cap24 is removed in the view shown in FIG. 2, revealing the battery chamberopening 32. A front panel 38 is shown removed from the remainder of thepump housing 14, allowing a view into the interior of the pump housing14. The drive assembly components and circuit boards of the pump 10 areremoved from the pump housing 14 in the view shown in FIG. 2. Acylindrical chamber wall 82 surrounds the cartridge chamber 80. Thebattery chamber 114 is positioned adjacent to the battery opening 32.

The front panel 38 defines a depression 39 for receiving a lens and anopening 43 for a display screen. The front panel 38 also defines adepression 41 for receiving a keypad and an opening 42 for facilitatingan electrical connection to the keypad.

A vent 36 is visible in FIG. 2 on the right end of the pump outerhousing 14. The vent 36 preferably incorporates a water barrier that isair permeable so that moisture is not allowed into the interior of thepump, but pressure equalization is possible between the interior andexterior of the pump. The use of a water barrier in vent 36 allowspressure equalization of a sealed environment within the pump housing14. The water barrier may be attached to an interior surface of the pumphousing 14 using a pressure sensitive adhesive. Adhesive capable of awater tight seal may be provided along perimeter 35 of pump housing 14to bond the pump housing 14 to the front panel 38 so that the pump 10can be exposed to water without allowing water into the pump interior.

Now referring to FIG. 3, the front panel 38 of the pump 10 is shownincluding a keypad 40 with individual buttons 45-48 for allowing a userto input information and make menu choices. The front panel 38 alsoincludes a display 44 present behind a lens 49, within the opening 43.In FIG. 3, an administration set is shown emerging from the pump cap 16.The administration set includes tubing 52 for delivering medication tothe body of a patient or user. The administration 50 also includes aconnector 54 for attaching the tubing to a medication cartridge withinthe pump. Often, a luer-lock connection is used between theadministration set 50 and the medication cartridge.

Now referring to FIG. 4, a front view of some of the components of thepump 10 within the pump housing 14 is shown, where the front panel 38has been removed. The cartridge opening 28 opens into the cartridgechamber 80. FIG. 4 shows a top view of the exterior wall 82 of thecartridge chamber 80. The cartridge chamber is where cartridges orsyringes of medication are placed for delivery to the patient. A driverod 88 is configured to move axially to dispense medication from acartridge in the cartridge chamber 80. The drive rod has a first end 92and a second end 94. At the second end 94 of the drive rod 88 aninterface cylinder 98 is defined for coupling to a plunger of amedication cartridge. A drive rod flange 100 is present at the second ordistal end 94 of the drive rod 88, and adjacent to the interfacecylinder.

The cartridge chamber 80 includes an open end at the cartridge opening28 and a closed end 102 opposite the cartridge opening 28. The closedend 102 of the cartridge chamber 80 defines an opening for allowing thedrive rod 88 to enter the cartridge chamber. The cartridge chamber alsoincludes a vent 108. The vent includes openings 110 to allow for thepassage of gas between the cartridge chamber 80 and the interior of thepump housing. The vent 108 may also include a gas permeable waterbarrier that covers the openings 110, similar to vent 36. Preferably,the vent 108 allows for pressure equalization between the chamber 80 andthe pump interior but prevents the passage of fluid. A watertight ventbetween the cartridge chamber 80 and the interior of the pump isvaluable because the pump components will not be exposed to any fluid inthe cartridge chamber, for example, if fluid leaks from a medicationcartridge.

The pump 10 also includes a battery chamber 114 having an open end atthe battery opening 32 that is closeable using the battery cover 24. Abattery within the battery chamber 114 is electrically connected to amotor 118. The motor rotates a motor gear 122. An idler gear 126 is inturn rotated by the motion of the motor gear 122. The idler gearinteracts with a drive rod gear 128 causing the drive rod gear to rotatewhen the idler gear 126 is rotated. The pump may also include avibratory motor 129 with a protruding structure 130 that is moved by themotor 129. The vibratory motor 129 can be used to call the user'sattention to the device. An audible signal may also be used to attractthe user's attention, alone or in combination with a vibration. Abracket 131 holds the driving motor 118 and the vibratory motor 129 inplace in the pump housing. A mount structure 132 for the vibratory motoris shown in FIG. 2.

In FIG. 4, the drive rod 88 is fully retracted, so that its first end 92is as close to the drive rod gear 128 as possible. In this fullyretracted position, the interface cylinder is as close as possible tothe interior face of closed end 102 of the cartridge chamber.Preferably, the flange 100 is contacting the chamber's closed end 102when the drive rod 88 is in the fully retracted position.

The interior face 134 of the closed end 102 is shown in FIG. 6. Theclosed end 102 defines a cavity 135 for holding an elastomeric sealingmember (not shown) to seal the opening in the closed end through whichthe drive rod passes. The drive rod flange 100 will preferably contactthe sealing member within the cavity 135 in the closed end 102 of thecartridge chamber 80.

FIG. 5 shows a front view of the components of the pump 10 similar toFIG. 4 but where the drive rod is at a different position. In FIG. 5,the drive rod 88 is partially extended into the cartridge chamber 80.

When the motor 118 operates, the drive rod gear 128 is rotated and thedrive rod 88 is axially moved. A lead screw 136 is connected to thedrive rod gear 128 and is rotated when the drive rod gear 128 isrotated. The lead screw 136 includes threads 138 on its outer surface.As can be seen in FIGS. 6-7 and 34, the first end 92 of the drive rod 88includes an opening 144 for receiving the lead screw 136. The lead screw136 is received within the drive rod opening 144 and extends within aninterior 146 of the drive rod 88. The drive rod 88 includes acylindrical shaft 148 and defines a cylindrical interior chamber 146. Atthe first end 92 of the drive rod 88, threads 149 are defined on theinterior surface of the drive rod 88 for interacting with the threads138 of the lead screw 136.

The drive rod 88 does not rotate as it is axially moved. Preventing thedrive rod from rotating as it is axially moved is important because ifthe drive rotates, it will not be axially moved by the rotation of thelead screw. The drive rod 88 is held in a fixed orientation by a clip154 that interacts with the outer housing 14. The drive rod 88 includesa recessed portion 152 at the first end 92. The clip 154 attaches to thedrive rod 88 at the recessed portion 152. The clip 154 prevents thedrive rod 88 from rotating when the lead screw 136 is rotated. As bestseen in FIG. 7, the clip 154 includes a U-shaped portion 158 that fitsaround the recessed portion 152 of the drive rod 88. The clip 154 alsoincludes a downward extension 160 that rides on a rib 164. The rib 164is a part of the pump housing 14 and extends along the length of thedrive rod and lead screw from the drive rod gear 128 to the closed end102 of the cartridge chamber 80. When the lead screw 136 rotates, thethreads 138 at the opening 144 at the first end 92 of the drive rod 88ride along the threads 138 of the lead screw 136, causing the drive rod88 to be axially moved.

Preferably, the interior chamber 146 of the drive rod 88 does not extendall the way through the drive rod 88 from the first end 92 to the secondend 94. As seen in FIG. 6, preferably a closure 166 is present withinthe interior 146. The closure 166 may be molded into the structure ofthe drive rod 88 when the drive rod is manufactured. Alternatively, aplug structure may be inserted into the interior 146 to provide theclosure 166. The closure 166 prevents any moisture or fluid fromtraveling from the cartridge chamber 80 to the interior of the pumphousing. The closure 166 could be a plug structure made of agas-permeable water barrier, which would provide a path for pressureequalization between the chamber 80 and the pump interior.

Medication Cartridge and Cartridge Interface with Drive Rod

Now referring to FIGS. 10-16, a medication cartridge is shown that maybe used with the pump 10 shown in FIGS. 1-7 and 9. The medicationcartridge 200 may include a cartridge barrel 202, a plunger 204 and acartridge rod 206. The cartridge barrel 202 is cylindrically shaped andincludes a closed end 210 and an open end 212. The closed end 210defines an orifice 216 through which medication can be delivered. Asseen in FIG. 11, the interior of the cylindrical cartridge barrel 202defines a medication reservoir 220 bounded by a barrel interior wall222. The cartridge barrel 202 may also include a cylinder 224 protrudingfrom the closed end 210. The cylinder 224 includes an exterior wall face226 and an interior wall face 228 shown in FIG. 15. Now referring toFIGS. 10, 11 and 15, the protruding end cylinder 224 surrounds aprotruding tip 232. The tip 232 protrudes beyond the cylinder 224 and isin fluid communication with the orifice 216 of the cartridge barrel. Onthe exterior wall 226 of the end cylinder 224, axial guides 234 aredefined. The axial guides 234 may be ridges molded into the structure ofthe protruding cylinder 224. Alternatively, the axial guides may bedepressions or grooves molded into the cylinder 224. The axial guides234 interact with the pump cap 16, as will be further described. Threadstructures 236 are defined on the interior wall 228 of the protrudingcylinder 224. The thread structures 236 are useful for securing anadministration set 50, as illustrated in FIG. 3, to the medicationcartridge 200.

In a preferred embodiment, the outer diameter of the cartridge barrel isabout a half inch, or about 540 thousandths of an inch, while the innerdiameter of the cartridge barrel is about 475 thousandths of an inch.The entire cylindrical barrel including the protruding cylinder and tipmay preferably be about 3 inches or less, more preferably about 2 inchesor less. Preferably, the maximum travel distance of the plunger from thefill line to the closed end is about an inch or less.

Now referring to FIGS. 9, 10, and 14, the plunger 204 includes acylindrical wall 250, a closed end 254, an open end 256, and a conicalface 258 at the closed end 254. The cylindrical plunger wall 250includes an exterior wall face 262 defining grooves 264 (FIG. 9) intowhich O-rings 266, 267 (FIG. 10) are seated. The O-rings 266, 267, sealagainst the interior barrel wall 222 of the medication cartridge barrel202. Now referring to FIG. 14, the cylindrical plunger wall 250 alsoincludes an interior wall face 268. A first tab 270 protrudes inwardlyfrom the interior face 268 of the plunger cylinder wall 250. In apreferred embodiment of the plunger of the present invention, a secondtab 272 also protrudes from the interior wall 268 of the plunger.Preferably, the first and second tabs are positioned opposite each otheron the cylindrical interior wall face 268.

The tabs 270, 272 are designed for mating with another structure that isused to move the plunger, such as a removable cartridge rod 206 forfilling or a drive rod 88 of a pump 10 for pumping. Many differentnumbers and configurations of tabs, or other protruding structures, maybe provided on the interior wall 268 of the plunger 204 to allow formating with another structure. For example, one, two, three, four, five,six or more tabs may be provided on the interior wall 268. Two or moretabs are preferred to one tab, and it is preferred that the tabs areevenly spaced around the interior wall face 268, so that force can beevenly applied to withdraw the plunger in the cartridge. The plunger 204is sized to be slidably received within the medication reservoir 220 ofthe cartridge barrel 202. The O-rings 266, 267 provide a sealingengagement with the barrel interior wall 222 so that the plunger can beused to push medication out of the medication reservoir 220.

Now referring to FIG. 16, the cartridge barrel 202 may include a fillline ridge 280 projecting from the interior barrel wall 222 near theopen end 212. The fill line ridge 280 provides a tactile indication ofthe fully retracted position for the plunger 204. As a user pulls theplunger away from the closed end 210, for example when filling themedication reservoir 220 with fluid, the rearmost O-ring 266 will comeinto contact with the fill line ridge 280. When the O-ring 266 contactsthe fill line ridge 280, an increased force will be necessary to furtherwithdraw the plunger past the fill line ridge 280. As the O-ring 266passes over the fill line ridge 280, a tactile bump will be felt by theuser. This indicates that the plunger should not be withdrawn further inthe medication reservoir. Optionally, the portion 282 of the cylindricalbarrel 202 that extends from the ridge fill line 280 to the open end 212may be shaded or textured. This shading or texturing may provide theuser with a visual indication of the fill line. In addition, the shadedor textured portion 282 may be useful in conjunction with a cartridgesensor that will be further discussed herein. Shading or texturing maybe provided on either the interior or the exterior of the barrel 202 atthe shaded or textured portion 282. FIGS. 10-11 and 15 illustrate ashaded portion 282 on the exterior surface of the barrel. FIG. 16illustrates a shaded portion 282 on an interior surface of the barrel.Alternatively, the shading or texturing could be incorporated into thematerial of the barrel 202.

The cartridge fill rod 206 shown in FIGS. 10-13 may be removably coupledto the plunger 204 and may be used to move the plunger 204 axiallywithin the cartridge barrel 202. The cartridge fill rod 206 may beespecially useful for filling the medication cartridge before insertingit into a pump. The cartridge fill rod 206 may be attached to theplunger 204 and then used to pull the plunger back in the medicationreservoir, thereby drawing in fluid. Then, the cartridge fill rod 206may be detached from the plunger 204 and the cartridge barrel 202 andplunger 204 may be inserted into a chamber of a pump.

The cartridge fill rod 206 includes a shaft 290 extending between aninterface end 294 and a handle end 298. A handle flange 302 at thehandle end 298 is useful for grasping and pulling or pushing thecartridge fill rod 206. The cartridge fill rod may also include aninterface flange 303 at the interface end 294. An interface cylinder 304may extend from the interface end 294 of the fill rod 206. The interfacecylinder defines a first channel 308 for receiving and retaining a tabof the plunger 204. The first channel 308 may include two portions forreceiving and retaining the portion of a plunger. The first channel 308may include a first axial portion 312 that is disposed parallel to anaxis of the cartridge fill rod 206. The first channel 308 may alsoinclude a first locking portion 314 that is disposed in acircumferential direction around the interface cylinder 304. Preferably,the junction of the first locking portion and the first axial portionforms a right angle. A portion of a plunger, such as a tab 270, is firstreceived in an axial portion 308 of the channel 312 as the fill rod ismoved axially toward the plunger. Then, the cartridge rod 206 is rotatedso that the tab travels along a circumferential locking portion 314 ofthe channel 308. Preferably, within the locking portion 314 of the firstchannel 308, a ridge 318 is defined. The cartridge rod 206 is rotated sothat the tab passes over the ridge 318 and is thereby more securelyretained within the first channel 308. The interface cylinder 304 mayalso include a ramp portion 320 associated with and adjacent to thefirst channel 304 for guiding a portion of the plunger into the firstchannel 308.

As best seen in FIG. 13, preferably, the interface cylinder 304 alsodefines a second channel 322 for receiving a second portion of aplunger, such as a tab 272. The second channel 322 may include a secondaxial portion 324 disposed parallel to an axis of the cartridge rod 206.The second channel 322 may also include a second locking portion 326disposed in a circumferential direction around the interface cylinder.The locking portion 326 may also include a ridge 328 over which the tab272 may be pushed as it is rotated into the locking portion 326 of thesecond channel 322. Preferably, the axial and locking portions of thesecond channel also form a right angle. A second ramp portion 330 may beassociated with the second channel 322 to guide a portion of the plungerinto the second channel 322. The interface cylinder 304 of the fill rodcould also include additional channels for receiving additional portionsof a plunger.

The ridges 318 and 328 within the locking portions of the channels 312and 322 may be sized so that they will contact the tabs of the plungerand configured so that they deform after the tabs of the plungers passover them. This deformation allows the tab to move farther into thelocking portion of the channel and provides the user with a tactileindication that the tabs are positioned in the locking portions of thechannels. The interface cylinder 304 may include a hollow portion 336 atits interface end 294, seen in FIGS. 12-13, which is useful infacilitating the molding process if the fill rod is molded.

Cartridge Interface on Pump

Now referring to FIGS. 4 and 8, the interface cylinder 98 of the driverod 88 includes a structure for coupling the drive rod 88 to a plungerof a medication cartridge, such as the plunger 204 shown in FIGS. 9,10-11 and 14. The interface cylinder 98 of the drive rod 88 may includea first channel 350 for receiving a tab of the plunger. The channel mayinclude a first axial portion 354 extending from the second end 94 ofthe drive rod in a direction parallel to the axis of the drive rod. Thefirst channel 350 may also include a first locking portion 356 extendingcircumferentially around the surface of the interface cylinder 98. Thefirst channel 350 may also have a first ramp 358 associated with it toguide a tab into the first channel. The interface cylinder 98 may alsoinclude a second channel 362 opposite from the first channel on theinterface cylinder 98. The second channel 362 may also include a secondaxial portion 366 that extends in a direction parallel to an axis of thedrive rod. The second channel 362 may also include a second lockingportion 368 extending circumferentially around the interface cylinder98. The second channel 362 may also include a ramp portion 370 forguiding a tab into the second channel 362, similar to the ramp 358associated with the first channel. The interface cylinder 98 could alsoinclude third, fourth or additional channels for receiving a portion ofthe plunger.

When a medication cartridge is loaded into the cartridge chamber 80, theuser first removes the cartridge rod 206 from the medication cartridge200. Then, the user inserts the medication cartridge 200 axially intothe cartridge chamber 80 through the cartridge opening 28. Themedication cartridge 200 is inserted axially until the plunger comesinto contact with the interface cylinder 98 of the drive rod 88. If thetabs 270, 272 of the plunger 204 are aligned with the channels of theinterface cylinder when the medication cartridge 200 is inserted, thenthe tabs will be received in the axial portions 354, 366 of the channels350, 362 as the cartridge is further axially inserted into the cartridgechamber 80. If the tabs of the plunger 204 are not aligned with thechannels of the interface cylinder when the plunger contacts theinterface cylinder, the tabs will be guided into the axial portions 354,362 of the channels 350, 352 by the ramps 358, 370 as the medicationcartridge 200 is rotated. If the pump is positioned with the cartridgechamber opening facing upward, then the cartridge is dropped into thechamber, and possibly with some rotation of the cartridge, the tabs 270,272 drop into the axial portions 354, 362 of the channels 350, 362 onthe interface cylinder 98 of the drive rod 88. Once the tabs 270, 272are positioned at the ends of the axial portions of the channels 350,362, the cartridge is rotated so that the tabs are positioned within thelocking portions 356, 368 of the two channels. Preferably, the pump ispositioned with the cartridge chamber opening 28 facing up duringloading so that the action of gravity may be used to help engage thetabs of the plunger with the channels on the interface cylinder 98.

Pump Cap

After the medication cartridge is inserted into the cartridge chamber80, the pump cap 16 may be reattached to the cartridge chamber opening28. The pump cap 16 is illustrated in FIGS. 1, 3, and 17-20. The pumpcap includes a pump or attachment end 410 closest to the pump and adelivery end 412. At the pump end 410 of the pump cap 16, an interiorcylindrical surface 413 is defined. Protruding from the interiorcylindrical surface at the attachment end are two opposing tabs 414.These tabs are used to attach the pump cap to a mating structure 416 atthe cartridge chamber opening 28, shown in FIGS. 4-5. In FIG. 1, thepump cap 16 is shown attached to the pump housing 14. The tip 232 of themedication cartridge 200 is shown within the delivery end 412 of thepump cap.

Now referring back to FIGS. 17-20, another interior cylindrical surface418 is defined at the delivery end 412 of the pump cap 16. Axial guides420 are defined in the interior cylindrical surface 418 at the deliveryend 412 of the pump cap 16. These axial guides may interact with axialguides 234 at the closed end 210 of the cartridge barrel 202. In oneembodiment, the axial guides 234 on the cartridge barrel are protrudingridges while the axial guides on the interior wall 418 of the pump capare grooves, as illustrated. However, these structures could be reversedso that grooves would be defined on the protruding cylinder 224 of thecartridge barrel 202 and protruding ribs would be defined on theinterior surface 418 of the pump cap 16. Alternatively, cooperatingridges may be formed on both the pump cap and the cartridge barrel end.The cooperating guides 234, 420 help ensure that the drive rod of thepump is securely attached to the plunger. When the pump cap 16 isrotated into attachment with the cartridge chamber opening 28, the axialguides 420 on the pump cap cooperate with the axial guides 234 on themedication cartridge to rotate the medication cartridge and plunger in adirection to secure the tabs of the plunger within the channels of theinterface cylinder.

If the plunger is already attached to the drive rod when the pump cap isrotated onto the pump cap opening, then the interacting guides 234 and420 will cause the cartridge barrel to rotate around the plunger, whilethe plunger remains fixed to the drive rod. Once the drive rod isattached to the plunger, the rotation of the pump cap does not cause anyaxial movement of the plunger relative to the barrel, so no fluid iscaused to be ejected from the barrel and no air is drawn into thebarrel.

When the pump cap 16 is removed from the pump housing 14, thecooperating guides 234, 420 cause the medication cartridge 200 to rotatealso. This rotation moves the tabs out of the locking portion of thechannels on the drive rod interface structure 98, thereby facilitatingremoval of the medication cartridge from the cartridge chamber.

On the exterior surface of the pump cap 16, gripping members 422 aredefined. The gripping members 422 may provide the user with structure tograsp when removing or attaching the pump cap. The gripping structures422 may also interact with a cap cover as further described herein. In apreferred embodiment, the gripping structures 422 are made of anelastomeric material. The pump cap 16 may include two materials such asa molded polymeric material and a molded elastomeric material. Theexterior wall surface extending between the pump end 410 and thedelivery end 412 is made of the molded polymeric material and definesopenings 425 that surround the gripping structures 422. The moldedpolymeric portion 424 is shown in FIG. 20. An elastomeric portion 426may be formed within the polymeric portion 424, so that the elastomericgripping structures 422 protrude from the openings 425. As seen in thecross-sectional view of FIG. 20, the polymeric portions 424 surround theelastomeric portions 426. A lower portion of the elastomeric portion 426may form a seal area 428 for interacting with the cartridge chamberopening 28 and with the closed end 210 of the medication cartridge 202.

Visual Indicator of Drive Rod Attachment to Cartridge

Now referring to FIG. 4, at least a portion of the interface cylinder 98may include a visual indicator to assist the user with confirming thatthe interface cylinder is properly attached to the plunger 204. Aviewing window 20, shown in FIG. 1, provides a view into the cartridgechamber 80. Preferably, the cartridge chamber 80 is made of a fairlytransparent material so that a user can view the interface cylinder 98within the chamber. When the plunger is not attached to the interfacecylinder, the visual indicator on the interface cylinder 98 will bevisible to the user through the window 20. However, when the interfacecylinder 98 is properly attached to the plunger 204, the visualindicator will be hidden within the wall 250 of the plunger 204. FIG. 9shows a view of the pump drive assembly where the plunger 204 isproperly attached to the drive rod 88. As a result, the interfacecylinder 98 is not visible. In FIG. 9, the cartridge chamber 80 is notshown so that the attachment to the plunger may be more clearlyillustrated.

The visual indicator on the interface cylinder may take a variety offorms. For example, a portion of or the entire surface of the interfacecylinder 98 may include a dark color, a pattern, a bright color, orother readily observable markings. In the embodiment shown in FIG. 4,the entire drive rod is a dark color, such as brown or black.Alternatively, at least the end of the drive rod may be bright pink. Inanother alternative, a black and white pattern is present on theinterface cylinder.

Cartridge Sensor

A pump according to the present invention may be provided with acartridge sensor 440 configured to confirm whether or not a cartridge ispresent in the cartridge chamber 80. In one embodiment of the invention,a cartridge sensor assembly 440 includes a light emitter 442 locatedopposite a light detector 444 across the cartridge chamber 80 at theclosed end 102 of the cartridge chamber 80, as shown in FIGS. 4-5, 21-22and 29. FIGS. 21 and 22 illustrate a pump housing 14 including the driveassembly components, circuit boards 450 and 452, and a medicationcartridge 200 positioned within the cartridge chamber 80. The closed end210 of the medication cartridge 200 protrudes from the chamber cartridgeopening 28 in FIG. 21. FIG. 22 is a cross-sectional view along line22—22 of FIG. 21, through the emitter 442 and the detector 444. A line454 connecting the emitter 442 with the detector 444 draws a chordacross a top portion of the cylindrical barrel 202 within the cartridgechamber 80. The chord 454 is provided in FIG. 22 for illustrationpurposes only, to show the path of light between the emitter 442 and thedetector 444, and is not part of the pump. The chord 454 does not passthrough the drive rod 88 or the plunger 204.

The sensor 440 is preferably positioned on the outside of the cartridgechamber 80. The detector 444 detects light from the emitter 442 throughthe partially transparent cartridge chamber wall when the cartridgechamber is empty. By positioning the sensor 440 outside of the cartridgechamber wall 82, the sensor 440 is less likely to be in contact withfluid or dirt which could affect its operation. As shown in FIG. 2, asupport 445 and a detent 446 are used to mount and position emitter 442.Similar structures can be provided to mount the detector 444.

When a medication cartridge 200 is present in the cartridge chamber 80,the open end 212 of the cylindrical barrel 202 will be adjacent to theclosed end 102 of the cartridge chamber 80. Accordingly, the end of thecartridge barrel 202 will interrupt the light transmission between theemitter 442 and the detector 444. The sensor 440 may therefore be usedto indicate whether a cartridge is present in the cartridge chamber 80.

Typically, a barrel 202 of a medication cartridge 200 is at leastpartially transparent so that the level of fluid within the reservoir220 can be viewed. However, at least an end portion of the barrel ispreferably sufficiently opaque that it interrupts light transmissionbetween the two sensors. An end portion 282 of the cartridge barrel 202may be textured or shaded in order to ensure that light transmission isinterrupted between the emitter 442 and the detector 444. The texturingor shading on the cylindrical barrel 202 of the medication cartridge maybe provided on an inside surface of the barrel 202, an exterior surfaceof the barrel 202, or throughout the material of the barrel wall. It isalso possible for the sensor 440 to be able to detect the cartridgebarrel 202 without any texturing or shading present at the end of thecartridge barrel. Preferably, most of the barrel is sufficientlytransparent to allow viewing of the medication level, while at least theend portion of the barrel is sufficiently opaque to interrupt lighttransmission between the emitter 442 and the detector 444.

Idler Gear Sensor

The idler gear 126 is intermediate between the motor gear 122 and thedrive gear 128 as shown in FIG. 23. According to one embodiment of thepresent invention, a sensor may be provided to determine whether or nota gear in the pump, such as the idler gear 126, is rotating as aconfirmation that the pump is operating normally. Components of an idlergear sensor are described with respect to FIGS. 23-29. A magnetic flag460 may be provided on a front face 461 of the idler gear 126 as shownin FIG. 24. The magnetic flag 460 may include a plurality of legs 462extending from the center of the idler gear to near an outer perimeterof the idler gear. To determine whether or not the idler gear 126 isrotating, a magnetic sensor 468 may be provided within the pump interiornear the magnetic flag 460, as shown in FIG. 23. The magnetic sensor468, for example, a Hall Effect sensor, can determine the magnetic fieldat a point near the idler gear 126. Therefore, as the magnetic field ata point near the idler gear fluctuates because of the rotation of themagnetic flag 460, the sensor 468 measures the magnetic field.

Preferably, the sensor 468 is spaced away from a point on the idler gearthat is near the outer diameter of the idler gear. In one embodiment,the magnetic sensor and magnet is configured so that the sensor detectsa magnetic field when one of the legs 462 is directly in front of thesensor and detects no field when one of the spaces between the legs 462is directly in front of the idler gear. As the idler gear rotates, thesensor outputs information indicating the magnetic field. In thisconfiguration, the sensor output is approximately a square waveindicating when the magnetic field is detected and when it is notdetected. This information can be used by a processor to confirm thatthe pump is operating properly, and to signal an alarm or appropriatemessage if desirable. The processor may also have an input from themotor 118 indicating the number of motor cycles, or encoder counts,occurring over time. Based on the number of times a magnetic field issensed at the magnetic sensor, the number of encoder counts, and thegear ratios, the processor can confirm that operation is normal.

The magnetic sensor 468 is preferably positioned on a circuit board 470.In order to provide accurate determinations of the magnetic field andconsequently the rotation of the idler gear, the magnetic sensor 468 ismaintained at a specific distance from the magnetic flag 460 on theidler gear 126. A bushing 476 may be used to provide a fixed distancebetween the magnetic flag 460 and the circuit board 470. The bushing,illustrated in FIGS. 23 and 26, includes a hollow cylindrical portion477 for receiving a shaft end 475 of the idler gear 126. The hollowportion 477 is defined adjacent to a first end 482 of the bushing 476. Asecond end 484 of the bushing 476 is situated opposite from the firstend 482. The second end 484 fits within the opening 488 in the circuitboard 470. Therefore the circuit board is spaced from the magnetic flag460 by the width W of the widest portion of the bushing 476.

Additional stability for the circuit board 470 may be provided by adrive mechanism chassis, shown in FIGS. 23, 27 and 28, that supports thethree gears of the pump. The drive mechanism chassis includes an opening492 for a shaft of the motor gear 122, an opening 493 for a shaft of theidler gear 126, and an opening 494 for a shaft of the drive gear 128. Inaddition, the drive mechanism chassis 490 includes a number of pins thatare used to support the circuit board 470. First pin 496, second pin 497and third pin 498 protrude from a front surface 500 of the drivemechanism chassis 490. The pins protruding from the drive mechanismchassis 490 may be received within openings in the circuit board 470. Ina preferred embodiment, a first pin 496 is received in a first hole 501on the circuit board. The second pin 497 and the third pin 498 arereceived in the second hole 502 and the third hole 503, respectively, ofthe circuit board 470. The drive mechanism chassis 490 may be secured tothe pump housing by screws through openings 512 and 513 on the chassis,corresponding to openings 515 and 516 on the rear of the pump housing,shown in FIG. 1.

In the embodiment show in FIG. 27, the pins 496, 497, and 498 have auniform outer diameter slightly less than the diameter of the openings501, 502, and 503 on the circuit board 470, so that the pins fit withinthe openings. In an alternative embodiment, the pins 496, 497, and 498each have a smaller diameter end portion and a larger diameter baseportion. The end portion of each pin fits into the openings 501, 502 and503. The larger diameter base portion provides a hard stop against whichthe circuit board 470 can rest. This configuration helps provide thecorrect spacing between the circuit board and the drive mechanismchassis.

Additional stability may be provided to the circuit board 470 byproviding a bracket 508 behind the circuit board 470. A resilient foamlayer 506 may also be provided between the circuit board 470 and thebracket 508 to push the circuit board 470 toward the bushing 476.

Pressure Sensor

Now referring to FIGS. 5-6, in a preferred embodiment of a pump of thepresent invention, a pressure sensor 550 is also included in the pump10. The pressure sensor 550 may be positioned behind the end 554 of thelead screw 136 that interfaces with the drive gear 128. If the drive rod88 encounters resistance as it advances into the cartridge chamber 80,then the lead screw 136 will be pushed back toward the drive gear 128.As shown in FIG. 6, the end 554 of the lead screw 136 contacts a strainelement 552 of the pressure sensor. The strain element 552 deflects as aresult of pressure from the lead screw. Preferably, the pressure sensor550 registers even very small deflections caused in the strain element552. For example, the pressure sensor 550 could be configured to allowthe strain element to deflect about 20 mils or less, more preferably 10mils or less, and most preferably about 5 mils before sending a signalto the pump's processor.

One reason the drive rod 88 might encounter greater than normalresistance as it advances in a cartridge is an occlusion in tubingconnected to a cartridge within the chamber. A blockage in a cannulainserted into a user or at the users infusion site could also bedetected by the pressure sensor. Preferably, the processor connected tothe pressure sensor alerts the user to a possible occlusion when thestrain element deflects.

As seen in FIG. 6, a portion of the lead screw 136 near end 554 issupported by the drive chassis mechanism 490. The lead screw 136 ispositioned within an opening 494 in the drive mechanism chassis 490.Within the opening 494, a Teflon support 556 surrounds the lead screw136. The Teflon support provides a low friction interface between thelead screw 136 and its support in the drive mechanism chassis 490 sothat the lead screw can more easily rotate and move axially toward thepressure sensor 550 when the drive rod encounters resistance. A topbracket 558 helps maintain the pressure sensor 550 in its properposition. The top bracket 558 includes an opening 560 that is alignedwith an opening 512 on the drive mechanism chassis. Bracket opening 560,chassis opening 512 and pump housing opening 515 may receive a screw orother structure for holding the top bracket 558 and the drive mechanismchassis 490 in a stable position with respect to the pump housing 14.

In one embodiment, the pressure sensor 550 is configured to detect anegative pressure in the system that would pull the plunger and driverod toward the open end of the cartridge chamber. A negative pressuremight occur if a vacuum was drawn on the cartridge or tubing, if themedication freely flowed from the cartridge, or if the cartridge wasremoved from the cartridge chamber. The lead screw may be spring-loadedso that it normally applies a force on the strain element 552. If thedrive rod was pulled toward the open end of the chamber by a negativepressure, the lead screw would apply less force on the strain element.The resulting deflection of the strain element toward the open end ofthe cartridge is communicated to the processor, and this information maycause an alarm or may be taken into account in pump operations, such asthe cartridge loading process.

Pump System

FIG. 30 is a functional block diagram illustrating one of many possibleembodiments of a medication pump, generally identified as 600. Amicroprocessor 602 is in electrical communication with and controls apump motor 118, a display 44, an audio alarm 608, and a vibratory alarm129. The pump motor 118 causes the actuation of the drive rod or drivemechanism 88 that pushes the plunger 204.

Other embodiments can use a microcomputer, or any other type ofprogrammable circuit, in place of the microprocessor. Further possiblefunctions of the processor and other pump components are described andillustrated in the following four commonly assigned co-pending UnitedStates patent applications, which were previously incorporated byreference: “Insulin Pump Having Missed Meal Bolus Alarm” U.S.application Ser. No. 10/087,460, now U.S. Pat. No. 6,744,350“Programmable Medical Infusion Pump Displaying a Banner” U.S.application Ser. No. 10/087,205, “Programmable Insulin Pump” U.S.application Ser. No. 10/086,641, now U.S. Pat. No. 6,852,104, and“Programmable Medical Infusion Pump” U.S. application Ser. No.10/087,449.

The display 44 can have many different configurations such as an LCDdisplay. The display 44 displays various items of information that areuseful to a patient or caregiver. The audio alarm 608 may be a beeper.Similar to other portable electronic devices such as a cellulartelephone, the vibratory alarm 129 provides an alarm when an audiblebeep would be disruptive. A user can selectively enable or disable theaudio 608 and vibratory 129 alarms. In one possible embodiment, however,both the audio 608 and vibratory 129 alarms cannot be disabled at thesame time.

The microprocessor 602 is in electrical communication with both a randomaccess memory (RAM) 616 and a read only memory (ROM) 618. The RAM 616 isa static RAM that stores data that can change over time such as pumpsettings and a historical log of events experienced by the pump 600. TheROM 618 stores code for the operating system and the applicationprograms. The ROM 618 can be any type of programmable ROM such as anEPROM. In one possible embodiment, the RAM 616 has about 500 kilobytesof memory capacity and the ROM 618 has about 2 megabytes of memorycapacity.

An infrared (IR) port 620 is in electrical communication with themicroprocessor. The IR port 620 may provide data communication with anexternal device such as a computer for programming an applicationprogram, programming pump settings, and downloading historical datalogs. The pump 600 can include other types of communication ports inplace or in addition to the IR port 620. Examples of other possiblecommunication ports include a radio frequency (RF) port or a port thatprovides a hard-wired data communication link such as an RS-232 port.The IR port 620 may be located within the pump housing as shown in FIG.29 and includes an IR emitter and an IR detector. The IR port 620 may bepositioned adjacent to two openings 624 and 626 in the pump housing 14,as seen in FIGS. 1 and 4, for allowing communication with the IR emitterand IR detector.

Again referring to FIG. 30, a real-time clock 622 provides a clocksignal to the microprocessor 602. An advantage of having a real-timeclock 622 is that it provides the program with the actual time inreal-time so that the application program can track and control theactual time of day that insulin delivery and other events occur.

A keypad 40 also provides input to the microprocessor 602. Althoughother possible types of keypads are possible, one type of keypad hasfour buttons and is a membrane-type of keypad, which provides resistanceto water and other environmental conditions. As explained in more detailbelow, the keypad 40 contains soft keys in that the function of the keyscan change as a user executes different menu selections and commands.

Other inputs into the microprocessor 602 include the pressure sensor550, which is sensitive to the pressure within a reservoir ofmedication, the cartridge sensor 440 which is sensitive to the presenceof a medication cartridge within the medication chamber, and the motiondetector or idler gear sensor 468, which detects motion of a gear.

The pump may also include a bolus button 25 for allowing the user toadminister a dose of medication. The depression of the bolus button 25may provide feedback to the user, such as a beep, a tone, or vibrationof the pump. The bolus button 25 communicates with the processor 602 toinstruct the processor to activate the pump motor 118 so that the driverod 88 is moved a specified distance, thereby providing the user with aspecified dose of medication. The bolus button 25 can be seen within thepump housing 14 in FIG. 1. The bolus button 25 fits within a bolusbutton cavity 37, best seen in FIG. 2.

Many elements of the pump 600 may be positioned within one or morecircuit boards within the pump housing 14. For example, themicroprocessor 602, the RAM 616, ROM 618, real-time clock 622, and adriver for the display 44 may be positioned on a circuit board. In apreferred embodiment, a top circuit board 450 is positioned above abottom circuit board 452 within the pump housing 14, as seen in thecross-sectional view of FIG. 22 and the exploded view of FIG. 35. Nowreferring to FIG. 35, the top circuit board 450 may include an opening454 and the bottom circuit board 452 may include a corresponding opening455. The openings 454 and 455 may receive a screw or other connectingstructure to allow the circuit boards 450, 452 to be secured to the pumphousing 14 via opening 515 in the pump housing 14 (FIG. 1). Preferably,top circuit board 450 is electrically connected to bottom circuit board452 using a flexible electrical connector. The electrical connector mayemerge from the bottom circuit board 452 at the connection location 456and then attach to the top circuit board 450 at a location above theconnect location 456.

Cartridge Detection and Loading Process

The cartridge sensor 440 at the rear most part of the cartridge chamber80 senses whether the rear edge of the cartridge is positioned at therear edge of the chamber 80. This information may be used to ensureproper operation of the pump. For example, if the cartridge is removedwhile the pump is running, an alarm will sound to protect againstnon-delivery or a free flow of medication. If a cartridge is present inthe chamber, but the pump is not programmed to deliver medication, analarm may be programmed to sound to notify the user that the pump is notrunning. If no cartridge is present in the cartridge chamber, the usercan be notified.

Information from the cartridge sensor 440 may also facilitate thecartridge loading process. An auto-loading process may be programmedinto the pump microprocessor 602 and assist the user in loading thecartridge. Information from the pressure sensor 500 or idler gear sensor126 may also be used in the cartridge loading process. FIGS. 31-33 areflowcharts illustrating one cartridge loading process. In order to loada new cartridge, first a user fills a new cartridge at step 650 andremoves the pump cap 16 at step 654. Any old cartridge already withinthe chamber 80 is removed at step 658, and the user selects the loadcartridge menu at step 702.

Alternatively, the pump may detect when a cartridge is removed as shownin step 659 and automatically enter the new cartridge menu as a result.There are situations where a user will want to remove the cartridgebriefly and then put it back in. For example, the user may want to checkfor air bubbles in the cartridge. The pump may be alert for thissituation and not enter the load cartridge menu if a user is removingthe cartridge only to check it, not to change it. For example, if thecartridge is more full than a certain threshold level, the pump mayassume that the user is checking the cartridge when the cartridge isremoved. However, to ensure the user is not unknowingly withoutmedication, the pump may alternatively warn the user and ask the user ifshe is checking the cartridge or changing the cartridge at step 700. Ifthe user responds that she is checking the cartridge, the pump maymaintain the drive rod in the same position, or may slightly extend thedrive rod so that it is easy for the user to reattach the drive rod tothe cartridge. If the user does not respond or responds that she ischanging the cartridge, then the pump may automatically enter the newcartridge menu at step 701. However, to ensure that the cartridge isproperly attached to the drive rod after a cartridge is checked, thepump may be programmed to automatically enter the new cartridge menuwhenever the cartridge is removed, as shown in FIG. 31. In this case,the pump may query the user at step 703 whether she is checking orchanging the cartridge, and may use the answer to that question later inthe loading process to determine the best initial loading position forthe drive rod.

Once the load cartridge menu is initiated, the pump checks the cartridgesensor 440 to determine if the rear portion of a cartridge is detectedat the rear of the chamber at step 704. Typically, no cartridge will bedetected at step 704 because the pump has not retracted the newcartridge and the old cartridge has already been removed by the user.

If no cartridge is detected, the motor may be activated to move thedrive rod to an initial loading position at step 706. The initialloading position may be fully extended, fully retracted, or somewhere inbetween, depending on the typical initial plunger position within thecartridge. One preferred initial loading position is between thestarting point and the ending point of the distance that the drive rodtraveled during delivery of the medication in the previous cartridge.Preferably, the initial loading position is approximately halfwaybetween the starting point and ending point for delivery during theprevious cartridge. For example, if the drive rod traveled about 1 inchduring delivery of the previous cartridge, the drive rod will beretracted about 0.5 inch at step 706. The automatic retraction of thedrive rod to an initial loading position is designed to save the user'stime when loading the cartridge. The pump is typically designed todeliver fairly small doses of medication over a long period of time. Thefill retraction and advancement of the drive rod can therefore take arelatively long period of time. By retracting the drive rod partially,the pump gets a head start on the retraction of the cartridge all theway into the pump.

It is also possible, though not preferred, for the pump to retract fullyto the rear of the chamber before the cartridge is loaded. Fullretraction is not necessary unless the new cartridge is completely full.If the new cartridge is not completely full, and the drive rod has beenfully retracted, the drive rod will have to be advanced in order for theplunger to be attached to the drive rod. Therefore, it is preferable tounderestimate the amount that the drive rod will need to be retracted inorder to pull the cartridge to the rear of the chamber. In addition, thepump system can take advantage of the fact that most users will fill newcartridges to approximately the level of the previous cartridge. Byretracting the drive rod half of this distance, the drive rod isunlikely to be retracted an unnecessary distance.

In determining the initial loading position in step 706, the pump maytake into account whether the user removed the previous cartridge inorder to install a new cartridge or merely to check the existingcartridge for some reason, such as checking for air bubbles. If the userpreviously responded at step 703 that they were removing the cartridgeto check it, then the initial loading position in step 706 may be thesame position or slightly extended from the position it was in when thecartridge was removed.

If a cartridge was detected at step 704, then the user is reminded tomake sure that the old cartridge has been removed. If the old cartridgewas not already removed, the user does so at step 710. The user attachesthe new cartridge to the drive rod interface structure 98 at step 710.The process used to attach a cartridge to the drive rod was previouslydescribed. Then the user selects a load cartridge command using thedisplay 44 and keypad 40 at step 714. The cartridge sensor 440 ischecked to determine if a cartridge is present at the rear of thechamber at step 718. The pump does not expect a cartridge to be presentat the rear of the chamber because the retraction process has not yetbeen initiated. If no, the steps illustrated in FIG. 32 are followed. Ifyes, the steps illustrated in FIG. 33 are followed.

If a cartridge is detected at the rear of the chamber in step 718,before the drive rod has retracted beyond the initial loading position,this indicates that possibly the old cartridge was never removed or thecartridge is less full than a minimum amount. Detection of a cartridgeat step 718 could also indicate that the new cartridge is considerablyless full than the old cartridge, such as less than about half of theprevious cartridge. In this situation, the cartridge might have beenfully inserted into the chamber without having the plunger engaged withthe interface structure 98. For example, if the previously deliveredcartridge was initially completely full and all of the medication wasdelivered, the drive rod traveled the full distance of the cartridgechamber during delivery of that cartridge. The initial loading positionof the drive rod for the next cartridge would be halfway extended.However, if the next cartridge was only one-eighth full, the cartridgecould be inserted fully in the chamber without contacting the plunger,resulting in detection of a cartridge although the plunger has not yetbeen attached to the drive rod.

If a cartridge is detected at the rear of the chamber in step 718, theuser is prompted to remove the cartridge at step 724. The user thenremoves the cartridge and acknowledges the removal at step 728. Thecartridge sensor 440 is again checked to see if the cartridge has beenremoved at step 732. If not, the process returns to step 724 where theuser is again instructed to remove the cartridge. If the cartridge hasbeen removed, the pump displays a message indicating that the user needsto wait at step 734 while the pump fully advances the drive rod at step738. By fully advancing the drive rod, the pump ensures that theinterface cylinder can be attached to the plunger regardless of thefullness of the cartridge. While the drive rod is filly advanced, theprocessor recalibrates the fully extended drive rod position to ensureaccuracy of future position calculations. The processor alsorecalibrates the drive rod position when it is fully retracted. Afterthe drive rod is fully advanced at step 738, the user is prompted toattach the new cartridge at step 710 and then selects a load cartridgeoption at step 714.

The pump may be calibrated to know when the drive rod is at fullextension and full retraction. By observing the encoder counts from themotor 118, the intermediate positions of the drive rod may also becalculated. The pump may calculate the beginning position of the driverod when a cartridge is initially loaded. By knowing the startingposition and the intervening encoder counts, the amount of medicationexpelled from the cartridge may be tracked by the pump.

If a cartridge is not detected at step 718, then the process illustratedin FIG. 32 is followed. The pump retracts the drive rod at step 742,which should now be attached to the plunger of the cartridge, until therear of the cartridge is detected by the cartridge sensor 440, the motorstalls, or the drive rod is fully retracted. The pump may also use thepressure sensor 550 to determine when the drive rod is fully retractedwhere the pressure sensor is pre-loaded to detect negative pressures onthe drive rod. If the cartridge is detected, the pump calculates thecartridge volume based on how far the drive rod was retracted before acartridge was detected at step 750. The pump begins a priming program,and prompts the user to attach the pump cap 16 and an infusion set tothe delivery end of the cartridge at step 754. Once the cap and aninfusion set are attached at step 758, the user initiates the primingprocess at step 762.

If at step 746, the motor stalled or the drive rod was determined to befully retracted through other detection methods before a cartridge wasdetected, then the pump displays an install cartridge alert at step 764.If this occurs, two possible causes would be that the user neverinserted a new medication pump or the cartridge sensor is notfunctioning properly. The cartridge sensor is again checked at step 766.If a cartridge is detected, the user is instructed to remove thecartridge at step 768 to confirm that the cartridge sensor is workingproperly. The pump checks for a state change at the cartridge sensor atstep 770 to confirm that the cartridge was removed. If the cartridge wasremoved, the pump fully advances the drive rod and recalibrates thedrive rod position when it is fully extended at step 772. Because of thepreceding cartridge sensor checks, the system ensures that there is nocartridge sensor in the chamber when the drive rod is fully advanced.The process then returns to step 710 on FIG. 31 where the user isprompted to attach a new cartridge.

Child Safety Cap

It may be desirable to configure the pump cap 16 to require somedexterity and strength to operate, so that it is difficult for a youngchild to open the cap. Now referring to FIGS. 38-40, in one embodiment,a safety cap cover 800 may be configured to snap over the standard pumpcap 16. The pump cap 16 is illustrated in FIGS. 1 and 17-20. The capcover 800 may have a first pump end 802 and a second delivery end 804.At both ends, the cap cover 800 preferably defines openings to allowpassage of an infusion set for attachment to the user. At the attachmentend 802, a lip 808 may be included that can fit around the pump end 410of the pump cap 16. The lip 808 may be discontinuous, as illustrated inFIG. 38, to facilitate snapping the cap cover 800 over the pump cap 16and removing it when it is no longer desired. A wall 809 extends betweenthe pump end 802 and the second delivery end 804, including a firstportion 810 of the wall that has a truncated cone shape. The wall of thefirst portion 810 is preferably sufficiently flexible so that an adultof normal strength can squeeze the first portion 810 of the cap cover toapply torque to the pump cap 16. When the wall of the first portion 810is squeezed, the cap cover 800 moves between a first shape or state anda second shape or state. In the first state, the cover 800 rotatesfreely around the pump cap 16. In the second state, the safety cap covercontacts the exterior surface of the pump cap so that the cap cover 800does not rotate freely. In the second state or position, the user mayapply torque to the pump cap 16 through the cap cover 800.Alternatively, the pump cap may be configured so that the user can pressdown on the cap cover 800 while turning the cap cover 800 to applytorque to the pump cap 16.

Structures on the pump cap 16 or the cap cover 800 can facilitate therotation of the pump cap 16. For example, the gripping structures 422 onthe exterior surface of the pump cap 16 shown in FIG. 17 may make iteasier for the user to grip the pump cap surface through the cap cover800. Preferably, the gripping structures 422 are constructed of anelastomeric material. Alternatively, or in combination with the grippingstructures 422, mating gripping structures 812 may be included on aninternal surface 814 of the first portion 810 of the wall 809 of the capcover, as shown in FIG. 38. The inclusion of gripping structures on thecap cover, pump cap, or both, prevent the cap cover from slipping as itis pressed against the pump cap.

In an alternative embodiment of a pump cap that is difficult forchildren to open, an outer shell similar to the cap cover 800 isintegral with the pump cap 16. The outer shell may rotate freely on thepump cap unless the outer shell is squeezed or pressed down while it isturned.

Belt Clip Attachment

An attachment device may be provided and used with the pump 10 that isuseful for attaching the pump to a belt clip or another holding device.One example of a belt clip attachment device 850 is shown in FIGS.36-37. The attachment device 850 includes a first protrusion 852 and asecond protrusion 854. The first protrusion 852 is configured to beinserted into a first slot 856 on the top of the pump housing 14, asshown in FIG. 1. The second protrusion 854 is configured to be insertedinto a second slot 858 on the bottom portion of the housing 14 as shownin FIG. 29. A main body portion 860 of the attachment device 850 restsagainst the back side of the pump housing 14, opposite the display area.The attachment device 850 may also include a third protrusion 862 thatcan be used to further support the pump 14 within the attachment 850.The device 850 may also include a pivot point 864. The pivot point maybe the point of attachment between the attachment device 850 and anotherstructure, such as a belt clip. The pivot point 864 may allow the body860 of the attachment device 850 to rotate with respect to the otherdevice to which it is attached. This rotation allows for maximum comfortof the pump user. For example, if the pump 10 is attached to a belt clipusing the clip attachment device 850, then the pump may be rotated tothe optimal position when the user is seated. The pivot point may bepositionable between several discrete positions. Belt clips that canreceive a pivot point similar to pivot point 864 are well known.

Alternatively, the pump may be positionable in one of severalorientations in the belt clip, but may not be allowed to rotate freelybetween those positions. Free rotation of the pump may cause kinking ofthe tube. In this scenario, the user would remove the attachment devicefrom the belt clip in order to move the pump to a different orientationrelative to the belt clip.

The various embodiments described above are provided by way ofillustration only and should not be construed to limit the invention.Those skilled in the art will readily recognize various modificationsand changes which may be made to the present invention without strictlyfollowing the exemplary embodiments and applications illustrated anddescribed herein and without departing from the true spirit and scope ofthe present invention which is set forth in the following claims.

1. A cartridge barrel for use in a medication pump comprising: acylindrical barrel wall comprising an open end and a closed end, whereinthe closed end defines an orifice, a cylindrical wall projecting fromthe closed end of the cylindrical barrel and surrounding the orifice,the end wall comprising an interior face, an exterior face, and axialguides on the exterior face, a tip at the closed end within the end walland in fluid communication with the orifice, and a ridge defined on aninterior face of the barrel wall, wherein the ridge divides the barrelwall into: an open end portion extending from the ridge to the open end,and a closed end portion extending from the ridge to the closed end,wherein the open end portion and the closed end portion do not overlapwith the ridge, wherein the open end portion includes only one unbroken,opaque band, wherein the opaque band is more opaque than at least aportion of the open end portion of the barrel wall.